1. Field of the Invention
The present invention generally relates to instruments for measuring fluid properties and, particularly, to a piezoelectric transducer for measuring properties of borehole fluids.
2. Description of the Related Art
In underground drilling applications, such as oil and gas exploration and recovery, a borehole is drilled into the earth. The drilling process can include taking measurements of fluids in the borehole while the borehole is being drilled (logging while drilling (LWD)). In some cases, a wireline is used to lower a measurement instrument into the borehole after a stage of the drilling process has been completed to measure properties of fluids in the borehole.
Measured fluid properties can include, for example, the density and viscosity of the fluid. The properties can be measured by placing a mechanical oscillator in the flow path of the fluid. Fluid density is measured primarily by measuring changes in the vibrational frequency of the oscillator while viscosity is determined primarily by monitoring the decay time of the resonance.
Other properties can be measured either directly or indirectly by utilizing speed of sound measurements taken in the fluid. These measurements are typically referred to as “sound speed” measurements and can be used, for example, to determine a gas-to-oil ratio (GOR) of the fluid.
Presently, there exist devices that can measure two of three of sound speed, density and viscosity. In particular, instruments exist that can measure density and viscosity or that can measure density and sound speed. Instruments that can be used to measure all three do not.